1. Field of the Invention
The present invention pertains to gas compression apparatus. In particular, it pertains to compressor apparatus of the free-piston type which utilizes gas in a driving or motor cylinder to compress gas in a driven or compression cylinder. More specifically, the present invention pertains to a free-piston type gas compressor of an improved and simplified design requiring a relatively low rate of gas consumption for use by the driving or motor portion.
2. Description of the Prior Art
The United States and other countries in their space programs have sought means to allow spacement to perform activities outside of the vehicles in which they are traveling through space. In the past, such extravehicular activities required the use of an umbilical cord from the vehicle to supply the spaceman with oxygen and other items necessary to support life. The umbilical cord limits the mobility of the spacemen and may create problems in design, manufacture and operation.
Recently, means have been sought to eliminate the umbilical cord. In one concept, a self-contained life support system utilizing high-pressure oxygen bottles in a manner similar to Scuba equipment for underwater divers has been proposed. If such a system is utilized, it is desirable to fill the oxygen bottles from a common source, such as the cabin oxygen supply. However, since the pressure of the cabin oxygen supply is typically 900 psia and the pressure required for the extravehicular activity oxygen bottles may be 4000 psia, some means of compression must also be provided. With the limited space and weight requirements of space vehicles and the limited energy available, the free-piston type compressor appears to offer certain advantages in compressing and transferring gas from one container to higher pressure containers.
Free-piston pumps or compressors are well known. Such pumps or compressors generally comprise a driving or motor piston or cylinder and a driven compressor piston and cylinder of smaller diameter. The pistons are connected by a rod member for mutual reciprocation within their respective cylinders. Fluid, gas or liquid, is generally supplied from a fluid source to the driving cylinder. Filling of the cylinder by mere displacement or expansion of the driving fluid forces the driving piston, and consequently the driven piston, through a cycle in which fluid is displaced and possibly compressed in the driven cylinder for transfer to a second location. Of course, one of the advantages of a free-piston type compressor is that its energy is provided by the fluid which it pumps or compresses, rather than requiring an outside energy source such as electricity or mechanical energy from an internal combustion engine or the like.
Examples of free-piston type pumps or compressors may be seen in U.S. Pat. Nos. 2,750,753 and 3,154,928. However, in each these devices, thermal energy must be provided to create the gas expansion required for operation of the pump or compressor. This requires an outside energy source.
U.S. Pat. No. 3,234,746 discloses a free-piston type gas pump which does not require thermal energy. However, in this device the free-piston apparatus merely transfers fluid from one storage container to another without an increase in the pressure thereof. Thus, its application is limited merely to a transfer function.